There are a lot of masks like these sold in dollar shops here in New Zealand. Plastic vacu-formed ones with elastic straps. Bats and skulls and witches and devils and pumpkins. All for $2.50 each (NZ Dollars). They are infact quite retro looking.

By the way, if any of you haunters want, I can put up photos of them up. And if you really want, I can buy some for you and ship them over.